p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 555

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

19.6
It is possible to switch between the user MAT and user boot MAT. However, the following
procedure is required because both of these MATs are allocated to address 0.
(Switching to the user boot MAT disables programming and erasing. Programming of the user
boot MAT should take place in boot mode or programmer mode.)
1. MAT switching by FMATS should always be executed from the on-chip RAM.
2. To ensure that switching has finished and access is made to the newly switched MAT, execute
3. If an interrupt has occurred during switching, there is no guarantee of which memory MAT is
4. After the MATs have been switched, take care because the interrupt vector table will also have
5. Memory sizes of the user MAT and user boot MAT are different. Do not access a user boot
four NOP instructions in the same on-chip RAM immediately after writing to FMATS (this
prevents access to the flash memory during MAT switching).
being accessed.
Always mask the maskable interrupts before switching between MATs. In addition, configure
the system so that NMI interrupts do not occur during MAT switching.
been switched.
If interrupt handling is to be the same before and after MAT switching, transfer the interrupt
handling routines to the on-chip RAM and set the WEINTE bit in FCCS to place the interrupt-
vector table in the on-chip RAM.
MAT in a space of 8 Kbytes or more. If access goes beyond the 8-Kbyte space, the values read
are undefined.
Switching between User MAT and User Boot MAT
<User MAT>
Figure 19.17 Switching between User MAT and User Boot MAT
Procedure for switching to user boot MAT:
Procedure for switching to user MAT:
1. Disable interrupts (mask).
2. Write H'AA to FMATS.
3. Execute four NOP instructions before accessing the user boot MAT.
1. Disable interrupts (mask).
2. Write a value other than H'AA to FMATS.
3. Execute four NOP instructions before accessing the user MAT.
<On-chip RAM>
Procedure for
switching to
user boot MAT
Procedure for
switching to
user MAT
Section 19 Flash Memory (0.18-µm F-ZTAT Version)
Rev. 1.00 Sep. 21, 2006 Page 517 of 658
<User boot MAT>
REJ09B0310-0100